Need Advice On The Size Of This Cake!!

Hi All!! I was wondering if anyone can help me, I saw this cake and would love to do something simiar for an upcomming baby shower, but I'm having trouble with the size of the cakes, I'm thinking it's 9,8,7 ? I've always done a 2in difference but I really like the look of this and I'm thinking its a 1in difference.. I would really appreciate any help..TIA

I would also say 1"difference, and I think they are double barrel tiers. That top cake is almost as high as it is wide - it could be a 10, 9, 8, that would be double tiers. Or a 8,7,6, with 1.5 tiers in each.